Astigmatic lens



W. C. GREENE.

ASTIGMATIC LENS.

APPucATmN mso Amm. me.

Patented Feb. 8, 1921.

W. C. GREENE.

ASTIGMATIC LENS.

APPucATwN man Amm, 1919.

3 SHEETS-SHEET 2.

W. C. GREENE.

ASTIGMATIC LENS.

WILLARD C. GREENE, 0F EAST GRANGE, NEW JERSEY.

ABTIGMATIC LENS.

Specification of Letters Patent.

Patented Feb. 8, 1921.

Application filed April 26, 1919. Serial No. 292,985.

To all 'whom 'it may concer/f Be it known that I, riunito C. GREENE, a citizen o lt the United States, residing at East Orange, in the county of vEsser and State oi New Jersey, ha ve invented certain new and useful Improvements in Astigmatic Lenses, of which the lollmving is u specification.

My present invention relates to ustigmatic lenticular systems.4 particularly such as are used on automotive vehicles and the like, for illuminating the highway within u prescribed aree. so that the driver of the vehicle may huye the approachini@v surface of treverse extendedly :and uderplately illuminuted, lwhile at thc saine tim(I the projected light benin is vlimited :ind controlled from disturbing` the vision ot drivers of approaching vehicles und likewise the vision of pedestrians.

(lne ol the objects ot my invention is lo provide n head lamp and-au astigmatic lenticular system therefor, which `.vill project a beam of novel cross-section and produce :L positive, e'licient illumination oli' the high- "'hile also effectively keeping the intense projected light beam below a. level at .any distance at which it will cause visual enuoyance to drivers of other vehicles und to pedestrians.

Another object of my invention isto pro- '.luce :i iniilti-refractive. ond multi-'focal lens ya heed-lmnp which Will so retract the rays reflected from the optical mirror of the head-light system esV to produce a 4certain desired illumination of 'the highway and which at the saine time, may be manufactured by pressing in molds with little or no tendency to produce surface distortions which common ,y r'esult from excessive 'Werpege and shrinkage produced in the pressing and :iniienlliuej` `opera-tions inthe lxfeelringl; of many pressed glass aJl-iclesjv I 'itlijthese end 'other ob ectsjinfifie'w, my invention consists 'of certain Hotel features of @metrufftitmf.y comhination'aid arrangement of parts as Willbe more fully described und pointed out in the appended claims.

A compound ormuljti-focal lens possessing the properties just described may be preferably constructed 'es a nitpti'cal part and may represent the homogeneous union of a single plano-spherical 'element of horizontal axis with a plurality 'of 'plano-conical, or

plano-conoiclel elements of'verti'cal axe-s.

` Such construction isloptlcall charct'erlstic of :isigle optical lilfelli@Ilfbv 'zitting onerefrectin'@ surface of constet'focallen th and' arial lilacinent, andthe other re ranting lar to Fig. l.; Fig. 3 is a diagrammatic front elevation ot' my novel multi-focal lens with points and planes marked thereon by which the diagrams of Figs. l und 2 were obtained; Fig'. -l n frag-mental. front elevation of the upper hall3 of e multi-focal lens which l have :ldopted tor purpose of illustration; Fig. 5 is :i fragment-nl, rear elevation of the lower half oi' the multi-focal lens shown in Fig. -lz Fig'. is :i section in the transverse, Vertical, median plane ll-Y of the multi-focal lens` as shown in Fig. 3, und Fig'. 7 is a section in the transverse. horizontal, medien plane Z-Z of the multi-focal lens lool-:iupr downward vfrom the center of the lens.

Corresponding parts ure referred to in the specifications and in the drawings by similar reference characters.

lfteferrinp,l first to my illustrative forni of lens which is shown in Figs. 3 to 7 inelusive, the multi-focal lens 10, es is usual in such construction for head-lamps having parsboloidal mirrors, .is circular in outline and is provided with :in :interior annular, llenge surface 15 and u` posterior annuler. flange surface lli, by which it may be held in the head-lamp in correct relation with the light source, with the reflector and in correct placement. As i'u similar constructions in the art, one or both flange surfaces. or annular spaces, when the lens is made circular, may be roughened as 'et 1i' to increase the holding contact with other mrt-s and prevent au undesired rotation oJ the lens. l

The anterior reflecting surface lil, is joined to the front flanged surface or annular space by a continuous, mitered, conical surface 14, of minimum measurement to effeet a reduction in thickness of the combined optical elements. The mitered, conical surface also serves both as a locating and as a contacting surface Wit-h the headlamp bevel edge.

The front fece or anterior refracting sur- :face 13, of the multi-focal lens 10, in the illustrated form, is continuous `and spherically convex in contour, and 'therefore refracting through all planes. l have found that the radius of this spherical surface may be varied within considerable limits 'and still enter into the desired optical relations with the radii oi the posterior surfaces. The rcfracting power of the anterior surface is preferably calculated to only slightly modify the retracting power of the multiple posterior surfaces. symmetrical or an additional refraction by the anterior, convex, spherical surface ot all light rays transmitted or retracted by the multiple, con care. posterior surfaces etlects certain de sircd corrections in the light bram formation, thereby further controlling distribution and increasing the uniformity ot illumination.

The radius ot' curvature ol' the spherical anterior surface may approximate the radii of curvature olf certain posterior surfaces, thus reducing the thickness ot the combined retraeting elements and leert-rising the weight. and surface dietorti Yarialionfi in the construction and reflecting lmiver ot the :interior surface muy he made :marmi ing to the optical and structural diflicultics` which a particular problem in illun'iinatilm may present. `For example. a cmieaye unter4 ior refracting surface may be employed to increase the refracting power ot the multiple posterior concave retracting surface or the spherical surface may be decentcred troni the optical. axis X-X through certain planes as a compensating element tor thiol: ness of parts or as an additional relracting element.

The rear tace o1' posterior rei'racting4 surA faces 18, 19. 20, 2l ol the multi-focal lf ns 10, in the illustrative form in Fig;-f. 2 to T inclusive is a composite surface termed by a plurality ot' horizontally arranged, ronlinuous, warped segment-s and zones of conin cal surfaces having vert-ical axes, such as may be made by revolving straight lines around a vertical axis. Such warped tracting surfaces may be either conical or conoidal surface sections of vertical axes and as particularly shown in Figs. 6 and T at 18, 19, 20, 21. they are concave segments and symmetrical Zones out from l'ustums of right circular cones of 1vertical axes and ot various sizes.

Further, the refracting surfaces itl, 19, 20, 21 may in practice he generated by slightly curved or irregular lines Without markedly modifying the optical properties of the composite refracting surface or departing from the nature of this invention.

Likewise the height of the different rcl'racting surfaces may be varied in any portion or may be varied in the entire posterior surface according to the refraction require ments.

The multiple Warped refracting .surfaces are structurally ioined together by other surfaces conveniently set at right angles to the faces of the refracting surfaces, and shown in the illustrative form of lens, particularly in Figs. 4, 5, G and 7 as the mit/e1' surfaces 22, 23, 24 and 25. Geometrically considered, the miter surfaces are approximately circular lunes or portions of the same, with converging' curved boundaries. When the posterior refracting surfaces lie in a common plane, the lune shaped surfaces undergo chances in length, width, angular placement, and warping, in a corresponding degree to the changes effected in the refracting surfaces.

Both refracting and miter surfaces are joined to the posterior flange surface 16, by a mitered, conical surface 26, being approximately concentric to the mitered conical surface 14.

The difference in angular values between all posterior retracting surfaces is preferably made to vary coincidently with the changes effected in the mean radius of curvature between all posterior relracting sin faces. Such coincident and progressive yariation may follow either entirely or partially a progressive .seriesl of a definiti mathematical order.

For instance, in the lens illustrated, the posterior refracting surfaces are portions ol the surfaces of a series of right, vertical cones having parallel axes, with the radius of the cone forming the surface 18 larger and the apex an le of such cone smaller than the axis an apex angle, respectively. of the cone forming the next surface below, and so on to the bottom ot' the lens at the surface 21. y

ln order to avoid interference or fusion of one Warped surface With another in the molding operation, and at the saine time, to avoid undue thickness of glass, I preferably adopt a minimum miter measurement and so arrange the surfaces from some common plane or surface, so that not only is this minimum miter Width maintained, but also a minimum thickness of a part through certain planes. Such an arrangement is shown in my illustrative form the effect obtained being best shown in Fligs. 6 and 7. The anterior refracting surface 13 of the lens is shown spaced laterally from the posterior refracting surface 18, to maintain a minimum miter measurement for the miter surface 22, and the refracting surfaces and miter surfaces intermediate to and including the refracting surface 19 are in coinpensated placement to maintain a predetermined minimum miter measurement. With out such compensation, the adjacent refracting surfaces might emerge in the pressing operation. Such compensation is obtained, in the form illustrated, by shifting the axes of the cones forming the upper, posterior, refracting surfaces so that such axes are not in alincnient but are in the same vertical plane containing the optical axisof the lens.

An optical prismoid` havingr a concave rcfrecting surface, cut from a solidoic rcvolution having maximum and minimum radii, such as the frustum of a cone, a trustum of a arabolic conoid or frustums of other solids of revolution having maximum and minimum radii with the opposing surface of the section cut plane, will possess the property of simultaneously 'reflecting in two or more right angle placed planes and will be of least thickness in the median ver'- ticel plane.

When an optical prismoid having these iefr'acting characteristics undergoes further development with the formation ci a plarality of mitered surfaces, which may ln` made by mitered sections to approximate :i continuous, an interval or a composite surface and further has homogeneously affixed upon the plane surface described an additional refracting surface` ol' spherical or other forni, the alicixinpy or union of such surface may add a desirable portion as a compensating or auxiliary reiracting surface to th optical prismoid. As for example, considerations of improvements in the reduction of thickness of parts and of weight, increase in mechanical strength, decrease or increase of refracting power in certain portions, increase of uniformity of resultant illumination, decrease in distortion and Warpage in the pressing and annealin operations and other considerations accor ing to the particular service to which the optical part is; to be adapted, may determine the necessity or desirability of employing a reflectingr anterior surface.

While it is preferable for service condi tions to place the continuous spherical surface exteriorly, the multiple Warped surfaces may be used exteriorly Without noticeibly altering the optical properties of the BDS.

Referring now to vthe character of light beam projected by an optical system emhedging my nove] multi-focal lens, ornel form of which lies-.justbeen described,12 isy the ,frantoi en autemotivc vehicle to which is attached usual head lamps 11 and 1l', each provided with a source of light and a reilector adapted to normally project a, light bem having substantially parallel rays.

In the lamp fronts are placed my novel lenses 10 and 10" which se re-fract the light rays projected from the reie'ctor as to prodicezalhtf beam havin a cross-section as illustra hy the dottedines at 8, which is a trmsversef section through the vertical ptane MMM but turned thrligh an arc of 9G esito'- the plane M-L- i Itfv-ill be seenl that this light beam cross? section approximates in general that of an isosrfstlflgle thdghtl'i sides are somewhat curved and the angles` are not sharply defined. rlhis novel light beam cross-section results from a marked horizontal contrae tion of the upper sectors, a marked herizontal expansion of the lower sectors, cmliined with a vertical expansion of a light beam circular in cross section, the intensity of which is made proportionate according to the reiracting power of the combined o)- tical elements. rPhe top of this novel lig 't beam is relatively narrow and composed of virtually parallel and horizontal rays. The vertical, horizontal and intermediate plane refraction, produced by the top refrecting surface, being' the minimum of the multivfocal lens, the light rays at that portion will he projected for the greatest dlstan'ce with least width, producing maximum ray concentration for maximum projection distance. ln a descending,r relation the light rays arc refra cted simultaneously downward and outward at increasing angles for the descendingr reflecting surfaces, so that the bottom of the light beam is broad and composed of horizmitalljfv depressed and diverging rays The vertical, horizontal and intermediair` plane refraction as produced by the bottom surface, being the maximum of the multifocal lens, the light rays at that portion of the beam will be projected for the least disr tance with greatest. width., producing minimum ray concentration for minimum pro jection distance. `Allowing for loss of light intensity duc tc angular dispersion of liglit source and distance of projection, a cncentrated form of illumination is obtained on the highway distant from the light source and a wide diffused type of illumination olo` tained adjacent to the source. At the vero tical plane N-N the highway will be illuminated to a. Width corresponding to the' base of the dotted, substantially triangular section shown at 9 to indicate a cross-section e'f the light beam in a plane N--N, haft turned through an angle of degrees, similar to cross-section 8;

Intermediate portions of the li ht beam represent intermediate degrees e vertical horizontal and intermediate planes of -refraction, therefore intermediate idistaces and widths of light beam p etnia.

The posterior reflecting* e ernrmtsl being arranged in a suitable single progressive re fructive series as at 18 19, 20, 21, the uniforme of light distributie projette@ by the mu Yti-focal lens upon the' highway is the resultant of a combined series relationship established between the anterior refractiii'g surface 13. and the posterior reractng sur# feces 18, i9, 20, 2i, and all intermediate surfaces. 1 1

It win be understood 'that when e pair-"cf lamps is used, the two light beams are psr'- tially merged es shown. in Figi. 2 and #het the total width ofl highway illumihetedfis the distance between the two head-lamps, plus the lateral extensions ot the light beams intersected by the highway.

In Fig. 3, I have drawn lilies R-lt, S2-5, 'll-'l, U--U and R'-It, i"-S', T'-'l", U'-U' and have taken points thereon, 1,2, 3, 4, 5, 6, 7 and 1',2', 3', 4', 5', 6', 7', to indicate approximate marginal light rays passing through the lenses l() and 1.0', and iu l*1 igs. 1 and 2, I have illustrated the direction in the vertical and horizontal planes V1which each of these marginal light rays will'take, For clearness of illustration in iig. 2, the marginal light rajvs emergingrat points 1,2, 3, 4 and points l', 2',3', 4' are V,those marginal rays from the upper half of Vthe multi-focal lens being projected by the headlanip, While those marginal light rays emergingV at points 4, 5, 6, 7 and points 4', 5', 6', T' are those marginal rays from the lower half of an identically similar multiA ifocal lens represented by dotted lines as heing projected from the head-lamp. Axial light rays are coincident with the optical axes X-X and X'-X'.

It' will be seen that the construction of my multi-focal lensis such that marginal light rays emerging at points l and l have the minimum 'vertical depression with minimum horizontal divergence, whereas the marginal light raysat points` T and 7' have the maximum vertical depression and maximum horizontal divergence of the rays illustrated. A. comparison of marginal light rays emerging at points 2, 2', and at points (l, 6', shows that the emergent light rays at points 2, 2'l have less vertical depression and less horizontal divergence than the emergent light rays at points 6, 6'. Likewise a similaidifferenceV exists between emergent light rays at points 3, 3 and points 4, 4' or between emergent light rays at points 4, 4` and points '5v5'.

light ray emergingthrough the ver- `tioahpiane. lY-Y `als in Fig. V3, will have av vertical depression only, While light rays emerging' through the ,planes .R4-R, S-fS. Tf-TsuU-fU and, RL-iR', S'--S', T'WT',

IIL-U Willfhave bothhorizontal depression and horiaontal divergence. Furthermore, it

is evident thatfthe .emergent light ray'sin eerJ tainfportions of the lens may be 4retracted inone planeonlyiand in other portions they may be*retracted simultaneously thron-gh Ytvvof ormore planesl Theresult ofthis eocm-v" binhition isrto 'oausle aidesired proportionate distrihutionfof light by which distant objeetsiin the Center Vot the highway will he wellfilflnminatecl 1by themore parallel, con.-

centrated portion of Athe light beam, While the highway nearthe vehicle will he WellI iliurninatedL to a considerable distance on either sideaofthedenter.ofthe highway by; the #Widely trdivegentl vportion of fthe light? 1 beam. l The lintrmeidiat'e distanoesfrepresent a gradual transition l'r'oni distant, narrow concentrated area of illumination to an adjacent broad diifused area of illumination.

While I have illustrated a specific form of multitonal lens and an optical system which will produce the results indicated, it Will he understood that the construction of the lenses, producing' these results, may lle varied without departing from my invention.

What I olaim and desire to secure by Letlerf; Patent of theUnited States is:

l. An astigmatic lens, having a `face foi-med of Warped surfaces, and an opposed convex face. thereby light is retracted simultaneouslyin right angled placed planes and through all intermediate radial and other planes.

2. An astigmatifr lens, having n face Vl'orined oi' warped. mitored surfaces. and an opposed ronvex li-ace, whereby light is rel'rafftefzl simultaneously in right angled placed planes and through all intermediate radial, and other planes.

An astigmatic lensY having one face 'formed h v a plurality of warped surfaces equivalent to :i surface section oiJ a solid oi3 revolution having;` maximum and kminimum radii and an opposed face equivalent` to a surface section oi. a solid of? revolution hav ing equivalent radii.

4. An astigmatio lens, having one face Mmposerl of a plurality ot Warped, mitered surfaces formed by surfaeeseetions of cones and :m opposed fare formed by a surface #notion of a sphere.

in astigmatie lens. having one face .miposed ot' a plurality of Warped surfaces Foi-med liv solids of revolution, having `rnaximoin and minimum radii and an opposed Face formed by a surface section cfa sphere.

(E. lin astigmatic lens having one face i omposed oil a plurality of Warped, mitered urfaces formed h vsurfaee sections of cones," joined together by circular lunes or lportions of thosame, and an opposed face formediby a surface section of asphere. f

7. An astigmatic lens havin-gra; face formed of a pluralityA of Warpedsurfaees" and an opposed convex` faemeaeli of 'said warped surfaces consisting of'a segment lof the surface of a cone with the apexes of the Cone downward and the apex angles of the cones increasing progressively in successive segments, from the top tothe bottom off-the lens, 'i ,L :t

8. An astigmatio lens having a face formed of a pluralityof Warped -Sjurfaces and an opposed convex face, eaoiof ysaid!4 Warped surfaces consisting ofla segnent lof the surfaoe of a coneaf'with the apexe's otithe cone dmvnvvard'arid the apei4 anglesf'ih cones increasing logressivelyfanli the radii oi` the `segments ieereasing progressively; i

l'WHiLARD C.' GREENE.-

It is hereby certified that in Letters Patent No. 1,367,960, granted February 8,

1921, upon the application of Willard C. Greene, of East Orange, New Jersey, for

an improvement in Astigrmztiey Lenses, an error appears in the printed specification requiring correction as follows: Page 4,1ne 97, claim 4, strike out the Word mitered; and that the said Ljetters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 22d day of March, A. D., 1921.

[SEAL] M. H. CoULsToN,

Umnmtss'ioner of Patents. Cl. 24U-48.4. 

